Monday, 24 November 2014

Waxing Poetic

Lost Wax Casting

Creating jewelry is done by three primary methods: stringing (beads or pearls - can be simple or very complex), fabricating (cutting, soldering, hammering, etc.) and casting with cuttlefish or lost wax. Today, I'm going to talk a bit about lost wax because I'm enrolled in a lost wax casting class with the Creative Jewellers Guild. See more here: <http://instagram.com/creativejewellersguild>

The process is fascinating but requires some special equipment (kiln and centrifugal or vacuum caster) that most artisan jewelers (including me) either can't afford or do not have space for.

Carving 101

Wax actually comes in several forms and can be carved, built up, extruded or molded. One of the easiest ways to create a piece of three-dimensional jewelry starts with carving the you want shape from wax.

This photo shows the very early stage of a ring I plan to cast. I started from a green wax ring blank which was a lot heftier than it is in the photo.

At this stage, I have used a saw to trim the shank down to a wearable thickness, then used a file to begin shaping the top and opening out the center for the ring size I want.

The material is very easy to carve — in fact, you have to be careful to avoid removing too much material or letting a tool slip, creating accidental "embellishments". If you do make mistakes, you can use heat to soften and melt wax to repair the damage — but it's a lot of extra work. This ring is going to end up with a pair of uprights to clasp a rotating silver ball I made years ago but never used (mostly because I wanted this design but couldn't think of a good way to fabricate it).

Next Stage, Refining the Shapes

After a number of hours spent filing and scraping with a series of knives and carving tools (one is in the photo), the ring is taking shape. As you can see, the opening for the rotating ball is now wide enough to accept the silver ball.

One of the most difficult parts of preparing the wax models is to get the finish you want on the relatively soft material. It only takes one casting experience to make you understand a simple truth: whatever is on the wax will be there on the silver. It's a whole lot easier to remove lumps and bumps from the wax then it is to file them off the silver! It takes lots of time (and several methods) to get a smooth, clean finish on the wax. One method involves passing the item through heat (flame, hair dryer) — very carefully. It gives a very smooth finish but it is totally possible to melt your lovely model into a useless blob.

Because you can cast several items (depending on size) in one flask, I also came up with a small tiki-inspired pendant. It is a mini version of one I made in a casting class several years ago.

My First Tiki

A friend bought the large tiki some time ago but I did keep a photograph of it. This is more than twice as large as the blue wax carving above but it shows how different textures — created on the surface of the wax model — will be perfectly recreated on the silver.

Casting Class, Week One

On Sunday, we met in the Lapidary/Silversmithing Studio at the Richmond Cultural Centre for the first class with instructor and Guild member, Walter Pinder. Week one involves final finishing of the waxes, attaching sprues, and capturing the waxes in investment (like Plaster of Paris, but very fine textured so it will capture all the details in the waxes).

My Waxes, All Sprued Up

Yes, sprued, not spruced!

Looks pretty ugly but, if I've done everything right, I will end up with the ring, the tiki and a simple, loosely shaped triangle — another pendant.

Here, the waxes are on sprues (the blue wax rods) that will conduct molten silver into the models after the waxes have been fully melted and burned out, leaving the negative of the shapes in the hardened investment. The spues are buried in red wax that will provide the pouring point. All are in a rubber base that fits very tightly onto a metal flask (open at both ends). The flask is a bit taller than the highest point on the assembled waxes. After I took this photo, I mixed a batch of the investment material with water. We used a vacuum machine to suck the tiny air bubbles out of the liquid investment, then set the flasks carefully into a cupboard to wait for next week when we will remove the rubber bases, melt the silver, do the pours and, hopefully, have new jewelry items. Alchemy.